Grounding strap improvement for round grounding outlet



Sept. 16, 1969 MARTIN 3,467,939

'GROUNDING STRAP IMPROVEMENT FOR ROUND GROUNDING OUTLET Filed March 1, 1967 nvvslv 70/? Eva 5R7- L, MARr/A/ United States Patent "ice US. Cl. 339-14 2 Claims ABSTRACT OF THE DISCLOSURE A single round grounding convenience outlet is provided with a novel grounding screw terminal on the device mounting strap permitting rapid low-cost manufacture.

The present invention relates to a mounting strap for use with a single round grounded convenience outlet. More particularly it relates to a strap having particular convenience of manufacture and use.

Round outlets for mounting in wall boxes have certain configurations which are standardized by Underwriters Laboratory as well as by the National Electrical Manufacturers Association in order that there should be some uniformity and interchangeability of devices of different manufacturers. Similarly, the wall plates mounted over the installed devices are of these uniformly interchangeable dimensions.

All of the power receiving contact screws of a single round grounded outlet must fit in the general contour of the rounded outlet and it has been conventional in order to meet these dimensional tolerances to place the ground ing contact screw, where the device is grounded, on the axis of the long dimension of the mounting strap. Two problems are introduced by this manner of locating the grounding screw. One is that the screw employed for mounting the strap of the device in wall boxes is aligned with the path of a screwdriver which would be employed to tighten the grounding screw in place. The second problem is that the staking of a grounding screw located in the strap along its longitudinal axis is cumbersome and expensive in that it requires a separate operation on the thread of the grounding screw after it has been installed in place in the strap. To stake the contact screw means to deform the end of the thread so as to inhibit or prevent its accidental removal as the device is being wired by unscrewing the contact screw until it falls loose from the device.

The staking operation is performed by so deforming the threads at the end of the screw that its accidental removal is prevented. This may be accomplished by a tool which performs a relatively small amount of deforming work on the end of the screw to expand the screw end to dimensions larger than permitted by the threaded hole in which it has been initially threaded or by scoring the threads of the screw at its end or in some similar fashion changing the thread spacing so that it may not be threaded out of the hole in the bracket in which it had been threaded prior to the staking.

It is accordingly an object of the present invention to provide an improved round grounding outlet having greater convenience of manufacture and of use.

It is the further object of the present invention to improve the method of manufacture of round grounding outlets to facilitate staking of the grounding screw Without the necessity of a separate operation for this purpose.

Additional objects and advantages of the present invention will be in part apparent and in part pointed out in the description which follows.

In one of its broader aspects the objects of the present invention are achieved by providing a grounded convenience Patented Sept. 16, 1969 outlet comprising a generally cylindrical insulating housing having blade receiving apertures in its face and being partially open at its back and side portions to receive a mounting strap and wire terminals in insulated relation to each other, the mounting strap being generally yoke shaped to receive said insulated housing and being contoured to be received in and to partially enclose the base and side openings of said housing, the side openings of said housing being undercut to limit outer movement of parts inserted therein through bottom openings of said housing, and said strap being provided with a screw terminal tab adapted for entry into a side opening of said housing, said screw terminal tab being displaced at an angle to the confronting portions of said yoke to permit a staking tool to have access between said fronting -portions to stake the threaded end of a screw as it is inserted into said terminal tab.

The description of the features and advantages of the present invention will be made somewhat clearer by reference to the accompanying drawing in which:

FIGURE 1 is an exploded perspective view of the outlet of the present invention.

FIGURE 2 is a plan view of the face of the outlet showing the terminal screw and a portion of the strap in phantom.

FIGURE 3 is a side elevational view of the device of FIGURE 2 from the side of the device in which the grounding screw terminal is mounted.

FIGURE 4 is a side elevational view of the side of the device opposite to that shown in FIGURE 3.

FIGURE 5 is a top plan view of the strap of the present invention showing the relationship between the grounding screw and a staking tool addressed to the threaded end of the screw.

Referring first now to FIGURE 1, a molded plastic housing 10, of suitable plastic such as phenolic, is provided at its face 12 with openings 14, 16 and 18 to receive the blades of a cap or plug into rectangular apertures and to receive the grounding blade into half rounded aperture 18. The combination screw terminal 20 and blade contact 22 is shown poised for entry into a side opening 24 in the side of the housing 10, a fibreboard insulator 26 is also shown poised to drop in to place behind the terminal 20 after it has been inserted into the housing 10 to provide insulating separation between the current carrying contact and the grounding strap 30.

A side opening 32 in the side of housing 10 is provided to receive a conforming upright portion 34 of the strap 30 and is also provided with a pair of undercuts 36 to receive and hold the edges 38 of the upright portion 34 of the strap 30. A neck 40 is provided at the junction of the upright and end portion 42 of the strap to permit the edge 38 to be held within the undercut 36.

A grounding terminal tab 42 is formed integrally with the strap 30 at an edge of the upright 44 and is disposed at an angle to the upright portion 44. A grounding terminal screw mounted in the tab 42 has a head 46 and a threaded shank 48. The end 50 of the screw shank 48 is staked as it will be explained with reference to FIG- URE 5 below.

The strap 30 is mounted in the housing 10 after the contact 22 and a second conforming contact not shown as well as the fibreboard are in place and after the grounding contact member 52 is inserted in a receiving slot in the reverse side of housing 10 to align the contact with grounding prong aperture 18. Screw 54 is inserted through opening 56 in strap 30 and opening 58 in contact 52 and threaded into a conforming hole in the back face of housing 10 to complete assembly of the outlet.

Referring now specifically to FIGURE 5 an elevation of the bracket 30 is shown with the screw driving tool 60 and the staking tool 62 poised to operate on the screw simultaneously. The necessity for a secondary operation on the screw after it is inserted in the strap 30 is eliminated by the cooperative relationship between the tabs and the other components particularly the confronting upright portions 34 and 44 of the strap as best seen in FIGURE 1. The advantages of this cooperation in permitting the formation of the strap without a secondary operation will be evident from comparison with a grounding screw mounted as most are conventionally on one of the uprights 34 or 44 of the conventional strap.

What is claimed is:

1. A grounded convenience outlet comprising a generally cylindrical insulating housing having blade receiving apertures in its face and having openings in its back and side portions receiving a U-shaped mounting strap and wire terminals in insulated relation to each other,

said mounting strap partially enclosing said back and side openings of said housing,

and a screw terminal tab having a tapped opening therein extending from an edge of one leg of said U-shaped strap and being received in one of said side openings, said tab being disposed at an angle to the face of said one leg whereby access is provided for a staking tool between confronting faces .4 of the legs of said U-shaped strap to permit staking the end of a screw disposed in said tapped opening.

2. The outlet of claim 1 wherein the side openings of said housing are undercut and receive the upright edges of said yoke shaped strap to limit outward movement of the upright portions of said strap.

References Cited UNITED STATES PATENTS MARVIN A. CHAMPION, Primary Examiner PATRICK A. CLIFFORD, Assistant Examiner US. Cl. X.R. 339133 

